In conventional shock attenuation systems for shoes, some shoes have springs set in the hollow interior of the insole, while some shoes have a circulating flow pressure controlling mechanism or a bi-directional flow pressure controlling mechanism. However, different people may have different body weights, and each person may undertake different activities, such as an ordinary walk or a strenuous exercise etc., Accordingly, there is a demand for a shock attenuation system, which is comfortable on the human body, and can be variable for different occasions and to suit or different people. Unfortunately, in prior art designs, the shock attenuation and damping-effect capability of the elastic insole is not adjustable, and therefore does not satisfy the user's requirements.